Return http statuscode 404 on unknown branch

Signed-off-by: Lars Hjemli <hjemli@gmail.com>
diff --git a/cgit.c b/cgit.c
index 64d95f9..19adadd 100644
--- a/cgit.c
+++ b/cgit.c
@@ -285,6 +285,8 @@
 	if (get_sha1(ctx->qry.head, sha1)) {
 		tmp = xstrdup(ctx->qry.head);
 		ctx->qry.head = ctx->repo->defbranch;
+		ctx->page.status = 404;
+		ctx->page.statusmsg = "not found";
 		cgit_print_http_headers(ctx);
 		cgit_print_docstart(ctx);
 		cgit_print_pageheader(ctx);